Preparation of iron compounds.



- UNITED STATES Prawns-Torsion;

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i nuns rams. caaarcx, or JOHANNESBURG, maANsvAAL} ELLIOT" s'r; MAURICE HUTCHINSON'AND ROBERT GOW RALSTOIN', EXECUTORS TESTAMENTARYOF SAID I I JAMES TAYLOR CARRICK, DECEASED, ASSIGNORS T JOHN LAWSON CAMERON, 0F

SLANGSPBUIT, FOXHILL, NATAL, SOLE EXECUTOR OF BASIL STUART PATTISON.

, PREPARATION or anon comrounbs.

' Britain, residing atthe New Club, J (mannesburg, Transvaal, have invented'new and useful Improvements in the Pre aration of Iron Compounds, of which the oll'owing is a specification. g

. An iron compound suitable for use as a pigment has been prepared by, among others, the following rocess. To a substantially neutral or slightly acid ferrous solution,- such as the waste pickle liquor obtained in galvanizing after its treatment with scrap 1ron,-there is'added a prescribed fraction of the quantity of ammonia necessary to precipitate the whole of the iron in solution; the mixture is then diluted and oxidized by blowing air into. it until it becomes yellow. Subsequently the liquid is boiled, the remaining fraction of the ammonia added and the mixture'boiled under pressure; what is described as a blue black magnetic oxid being thereby produced.

The purpose of the present invention is to provide a process for the roduction of a pigment of this character which may be carried out in the cold and at normal pressures, thus, inter alia, doing away with the expensive cast .iron boilers which'have hitherto been necessary for efiecting the final boiling under pressure, and which in practice are very rapidly corroded by the ammonium salts contained in the liquors.-

A further purpose is to provide for the economical recovery of hydrochloric acid, in the case where ferrous chlorid liquors-are being treated. v 1

The specification of the. above described process points. to the conclusion that the yellow product obtained by oxidation after the first precipitation by ammonia is substantially ferric hydrate, and similarly upon adding the rest'of the ammonia ferrous hydrate is produced. Thus the penultimate roduct would appear to be a mixture of erric hydrate and ferrous hydrate, which substances are combined by the boiling under pressure.

In the specification of the above described liquor were saturated inthe first instance process it is stated that if all the ferrous but the present invention is based upon the discovery that by the addition of ammonia in the first instance in sufficiently large excess, a single and different reaction is brought about without the aid of heat or pressure, the immediate product of which is a blue black magnetic oxid, or hydrate of' iron, or combination of oxid and hydrate. The simplest method of carrying out the present process thus consists in adding the ammonia-as hydrate or carbonate-to the slightly acid solution, in large excess relatively to the total acid present, whe her combined or uncombined. Theminimum possi- Patented Qnu 4, 1911.

ble excess; is found to vary in accordance with the degree of concentration of iron in the total ,amount'of liquor which is vto-be oxidized. Thus with 3per cent. o'ffiron in the total solution, the-minimum amount of ammonia required is twice the equivalent quantity necessary to liberate the iron; and with higher precentages of iron more ammonia equivalents are required. Thfl'lil'llit,

ing case is found occur with about 1% per cent. of 1IOI1,' in whlch case the reaction may be eifecte'd with about 11; equivalents of ammonia. With less than li per cent. of iron, the requisite ammonia equivalentsincrease at a very rapid rate. After the addition of the ammonia, the solution is thoroughly oxidizedpas by aspiratin air through it for about 24 hours, the erroferric compound being thereby precipitated. The above operations are most advantageously carried out in the cold and at normal pressure. It

is found however that .by boiling the ammoniacalsolution prior to the removal of the precipitate therefrom the stabilit of the resulting pigment is increased. the process in a commercial sense, the ferroferric preci itate 'is removed by an electromagnet or y filtration, washed, and dried in the absence of air. The resultant product is a blue black-magnetic pigment. The ammonia in the filtrate is recovered or re enerated by any known and convenient met 0d such as the eva oration .of the solution or the addition of ime, boiling of the solution and collection in towers of the ammonia gas In the case where'the' original liquor is a solution of chlorid of iron, the hydrochloric acid is recovered as follows. Lime having 0 complete a been added to set free the ammonia as stated which mixture is evaporated at about 130 C above, or being added specially if necessary, and a solution of calclum chlorid thereby produced,'sulfu ric acid is added thereto in slight excess. 'By this means calcium sulfate and free hydrochloric acid are formed,

a by or while drawing air over it. It is found that by this means no trace of hydrochloric acid remains with the slightly acid residual hydrated 'calcium' sulfate, when, tested with 130 C. referred to is below producing the required degree ,0

silver nitrate solution. The temperature of that at which calcium sulfate dehydrates, and above that at which hydrochloric acid evaporates at normalpressure, but other temperatures between the corresponding limits may be used with reduced acid WhiChdlStllS over after the excess water issubstantially of the strength re uired'for pressure. The hydrochloric pickling purposes. The hydrate calcium sulfate produced by this means forms a marketable by-produch An important advantage 'of the present is met in process is that while no difficultfv d oxi ation,

' there is on the other hand no danger of overblowing, as-the aspiration-can be continued,

in presence of the excess ammonia, for days after the, reaction is complete, without a1- teration of the black. precipitate; and no tests are required tobe made during the operation, as in some known processes.

The process is applicable to the treatment of waste liquor. resultin from the pickling of iron prior to galvaniz1ng,or other ferrous solutions, whether waste or prepared specially for the purpose of the invention.

In my'co-pending application Serial No.

462 144, I have described and claimed the herein described reaction as applied to the separation of iron and nickel out of liquor obtained by the digestion of nickeliferous mattes. To such separation process no claim is'made in the present application.

What I claim, and desire to secure by Letters Patent is 1. The process of treating a ferrous solution for the production of a blue-black pi ment which consists in adding to the acid or neutral ferrous solution an ammonium compound indarge excess and afterward subjectin the mixture to prolonged oxidation, sai process being carried out entirely in the cold and under normal pressure.

2. The process of treating a ferrous solution for the production of blue-black pigment which. consists in adding to the ac1d or neutral ferrous solution ammonium hydrate in large excess and afterward subjecting the mixture to prolonged oxidation,

said process being carried out entirely in the cold and under normal pressure.

3. The process oftreatin a' ferrous solution for the production 0 blue-black pigment which consists in adding to the acid 

